1. Field of the Disclosure
This disclosure relates to a fabricating method of a liquid crystal display (LCD) device adapted to reduce a number of mask processes.
2. Description of the Related Art
In general, LCD devices control the light transmittance of a liquid crystal with a dielectric anisotropy using an electric field, in order to display an image. The LCD devices are usually fabricated by combining a color filter array substrate with a thin film transistor array substrate in the center of a liquid crystal layer.
Recently, LCD devices of several new modes have been developed in order to resolve a narrow viewing angle of the related art LCD device. LCD devices with wide viewing angle characteristics are classified into an in-plane switching (IPS) mode, an optically compensated birefringence (OCB) mode, a fringe field switching (FFS) mode, or others.
Among the LCD devices with the wide viewing angle, the IPS mode LCD device allows a pixel electrode and a common electrode to be arranged on the same substrate so that a horizontal electric field is induced between the electrodes. As such, major axes of liquid crystal molecules are aligned in a horizontal direction with respect to the substrate. Accordingly, the IPS mode LCD device has a wider viewing angle than that of a TN (Twisted Nematic) mode LCD device of the related art.
FIGS. 1A through 1G are cross-sectional views illustrating a method of fabricating an IPS LCD device according to the related art.
Referring to FIGS. 1A through 1G, a gate electrode 11 and a gate pad 13 are formed in a TFT (thin film transistor) formation region of (or distinguished from) a pixel region and a pad region by depositing a conductive metal on a substrate 10 and patterning the deposited metal. The substrate 10 is defined into a display area corresponding to a plurality of pixel regions and a non-display area corresponding to pad regions. The conductive metal for the gate electrode and pad 11 and 13 is selected from a conductive metal group including aluminum Al, an aluminum alloy (AINd), copper Cu, tungsten W, molybdenum Mo and so on.
Subsequently, a gate insulation film 12, a semiconductor film 14 and a source/drain metal film 15 are sequentially formed on an entire surface of the substrate 10 provided with the gate electrode and pad 11 and 13. The gate insulation film 12 is formed by depositing at least one material selected from an inorganic insulation material group which includes silicon nitride SiNx and silicon oxide SiO2. The semiconductor film 14 includes amorphous silicon (a-Si:H) and an impurity-doped amorphous silicon (n+a-Si:H).
Thereafter, first and second photo resist patterns 50a and 50b are formed on the TFT region and a data line region through a photolithography process, respectively. The first and second photo resist patterns 50a and 50b are prepared by forming a photo resist film on the entire surface of the substrate 10 and performing a half-tone or a diffraction mask process for the photo resist film.
Subsequently, as shown in FIGS. 1C and 1D, an etching process using the first and second photo resist patterns 50a and 50b as a mask is performed for the source/drain metal film 15 and the semiconductor film 14, so that an active layer 14a including a channel layer and an ohmic contact layer and source/drain electrodes 17b and 17a are formed on the gate insulation film 12. At the same time, a data line 25 is formed in the data line region and an active pattern 14b is formed under the data line 25.
In this way, when a TFT configured with the gate electrode 11, the active layer 14a and the source/drain electrodes 17b and 17a is formed on the substrate 10, a pixel electrode 19 is formed by depositing a transparent conductive material on the entire surface of the substrate 10 and etching the deposited transparent conductive material according to a photolithography process.
Afterword, a protective film 18 is formed on the substrate 10 provided with the pixel electrode 19 thereon, as shown in FIG. 1D. The protective film 18 can be formed by depositing at least one material selected from an inorganic insulation material group which includes silicon oxide SiO2 and so on.
Next, a third photo resist pattern 60 is formed on the protective film 18. The third photo resist pattern 60 can be prepared by forming a photo resist film on the entire surface of the substrate 10 provided with the protective film 18 and exposing and developing the photo resist film according to a photolithography process.
When the third photo resist pattern 60 is formed, an etching process using the third photo resist pattern 60 as a mask is performed for the protective film 18. In accordance therewith, a contact hole 40 exposing the gate pad 13 on the pad region is formed.
After the contact hole 40 is formed, a common metal film 30 and a fourth photo resist pattern 70 are sequentially formed on the entire surface of the substrate 10, as shown in FIG. 1F. The common metal film 30 is formed of a transparent conductive material. The fourth photo resist pattern 70 is formed on the common metal film 30 through a photolithography process.
Thereafter, as shown in FIG. 1G, an etching process using the fourth photo resist pattern 70 as a mask is performed for the common metal film 30. In accordance therewith, a common electrode 31 is formed on the protective film within the pixel region, and a gate contact pad 35 is formed on the gate pad 13.
In this manner, the method of an IPS mode LCD device according to the related art includes first through fifth mask processes. The first mask process is used for forming the gate electrode and the gate pad. the second mask process is used for forming the active layer and the source/drain electrodes. The third mask process is used for forming the pixel electrode. The fourth mask process is used for forming the contact hole. The fifth mask process is used for forming the common electrode.
Each of the above-mentioned mask processes can be completed by: forming a material film for a desired pattern on a substrate; forming a photo resist film on the material film; exposing the photo resist film in a desired shape using a mask; partially stripping the exposed photo resist film to provide a desired photo resist pattern; and removing the material film exposed by the photo resist pattern, in order to pattern the material film in a desired shape.
As such, the mask processes force a washing process, a deposition process, a stripping process, and an etching process using a liquid chemical agent to be repeatedly performed. Moreover, after the deposition process is performed within a chamber, the processes that make the substrate externally exposed continue to proceed.
As described above, if the fabricating processes of an LCD device increase, it is common for the substrate to include pollutants during the fabrication of the LCD device. Due to this, the characteristics of the TFTs deteriorate.
In view of this point, it is necessary to reduce a number of the mask processes. The reduction of the mask processes may allow several extra processes to be similarly reduced. As such, it can prevent elements from losing quality due to the pollution of the substrate.